Affective Responses to Exercise are Dependent on Intensity rather than Total Work MARCUS KILPATRICK 1 , ROBERT KRAEMER 2 , JOHN BARTHOLOMEW 3 , EDMUND ACEVEDO 4 , and DENISE JARREAU 2 'School of Physical Education and Exercise Science, University of South Florida, Tampa, FL; 2 Department of Kinesiology and Health Studies, Southeastern Louisiana University, Hammond, LA; 3 Department of Kinesiology and Health Education, University of Texas, Austin, TX, 4 Department of Health and Human Performance, Virginia Commonwealth University, Richmond, VA ABSTRACT KILPATRICK, M., R. KRAEMER, J. BARTHOLOMEW, E. ACEVEDO, and D. JARREAU. Affective Responses to Exercise are Dependent on Intensity rather than Total Work. Med. Sci. Sports Exerc., Vol. 39, No. 8, pp. 1417-1422, 2007. Purpose: The purpose of the study was to compare affective responses for two bouts of cycle ergometry with differing duration and intensity, but equal total work in kilocalories. Methods: Thirty-seven participants (20 male, 17 female, mean age 23.9 yr) completed a multistage cycle ergometer protocol to determine ventilatory threshold (VT) and peak oxygen consumption (mean = 34.9 mL-kg1-min-1). Two cycling trials were prescribed: 30 min at 85% of VT (50.1% •102 reserve) and an average of 24 min at 105% of VT (64.7% (lO2 reserve). The length of the 105% of VT bout was adjusted to yield equal total work in each exercise trial. Results: Using repeated-measures ANOVA, heart rate and exertion were significantly higher, and affective valence was significantly less positive (P < 0.01) for the higher-intensity, shorter- duration bout, with no differences in felt arousal (P > 0.05). Additionally, affective valence became less positive during the higher- intensity bout (P < 0.01) but not the lower-intensity bout (P > 0.05). Conclusion: These data extend previous findings by showing that the decline in ratings of pleasure during higher-intensity exercise is not dependent on differences in total caloric,expenditure. Additionally, results from this study support continued promotion of prescriptions that focus on exercise intensity that does not exceed the VT. Key Words: AFFECT, VALENCE, AROUSAL, EXERTION iven the clear health and fitness benefits of aerobic exercise, one would expect that regular exercise participation would be the norm. However, epide- miological data indicate that most American adults do not meet recommended levels of exercise participation. Specifi- cally, 23% of American adults participate in light to moderate physical activity five or more times each week, and 15% of Americans participate in vigorous physical activity three or more times per week (24). These rates are far below the 30% target figures set forth for each physical activity level in current recommendations for Americans (24), and they represent a public health problem of great significance with respect to physical activity behavior. Address for correspondence: Marcus Kilpatrick, Ph.D., School of Physical Education, Wellness, and Sport Studies, University of South Florida, 4202 East Fowler Avenue, PED 214, Tampa, FL 33620; E-mail: mkilpatrick@ coedu.usf.edu. Submitted for publication September 2006. Accepted for publication March 2007. 0195-9131107/3908-1417/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE® Copyright © 2007 by the American College of Sports Medicine DOI. I0.1249/mss.0b013e3!806ad73c Currently, two rather distinct sets of recommendations are made available to the public from the American College of Sports Medicine (ACSM), the U.S. Centers for Disease Control and Prevention, and the Office of the Surgeon General (2,3,19,23). The earliest recommendations devel- oped by ACSM were based on the assumption that more intense exercise and associated fitness improvements were prerequisites for health (2,3). In contrast, contemporary recommendations based on public health objectives recog- nize the value of physical activity that improves health status without significant fitness increases (19,23). These contemporary public health-oriented recommendations reflect a lowered minimum intensity (from 50 to 40% of maximal oxygen uptake reserve), increased exercise fre- quency (from 3-5 to 5-7 d'wk-1), and more flexibility in the achievement of exercise duration (from continuous to an accumulation of intermittent activity) compared with the original fitness-oriented guidelines. Thus, although the total caloric expenditure of the original and the more recent recommendations remain largely unchanged, the means for achieving the expenditure has evolved from a model based on cardiorespiratory fitness to one that is more intimately connected to general health promotion. This more contem- porary view reflects a trend to embrace the health and fitness benefits of low- and moderate-intensity physical 1417